andrew wrote:Yes, the digital signals from your Arduino to the LCD need to have a ground reference. Similarly your power supply for the LCD needs a ground return path. As both the Arduino and the power supply will then be both grounded to your LCD, their grounds are effectively connected together.

I'm new to the world of Arduno and treated myself to an Uno+ and I2C after Xmas for a bit of a project.

I've had a problem trying to get the I2C to display text and up until now it would only power on, illuminate but no text displayed. I only just realised there's contrast adjustment on the back of the LCD and after turning it have managed to get text to be barely visible but nothing better. I've adjusted through the full range from one direction to the other but it's only visible at single narrow point.

Is there anything I can do to make the display contrast greater?

Thanks,
Jon

** Update
Disregard that, I'm an idiot and connected the VCC pin on the LCD to the 3.3V 3V3 pin... needless to say connecting it to the correct 5V pin resolves the above issue.

I am working with the smart LCD module in AT mode.
When I wanted to print a variable it did not respond.
After some trial end error I did find the following solution:

Serial.println("AT+RC=0,2"); // Set cursor to first line position 3
Serial.println("AT+PR=Temperature");
Serial.println("AT+RC=1,2"); // Set cursor to second line position 3
Serial.print("AT+PR="); // Send AT print command
Serial.println( tempC, 1 ); // Print temperatue with one decimal
Serial.println("AT+PR= Celsius");